Formable reinforcing bar and method for making same

ABSTRACT

A formable reinforcement bar, a process for producing a formable reinforcing bar and a supported structure including a formable reinforcement bar are provided. The reinforcement bar includes a body portion of a fiber reinforced thermoplastic material. The process involves laminating multiple layers of thin strips or bundles of fiber reinforced thermoplastic to produce the formable rebar. The formable rebar may be produced at remote locations such as a construction site. The supported structure includes a composite material having a formable rebar embedded therein.

CROSS-REFERENCE TO RELATED APPLICATION

This is a request for filing a continuing application under 37 CFR 1.60of pending prior application Ser. No. 08/762,482, filed Dec. 9, 1996,now U.S. Pat. No. 5,650,280, which is a continuation of Ser. No.08/451,591, filed May 26, 1995, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a formable reinforcing bar for structuralsupport in construction applications and a method for making a formablereinforcing bar. More particularly, this invention relates to a formablereinforcing bar of a fiber reinforced thermoplastic material.

Reinforcing bars, or rebars, are employed for structural support in awide number of construction applications. For instance, rebars areincorporated into concrete and various other materials in theconstruction of bridges, buildings, roadways and the like to provideadditional support.

Traditionally, rebars have been manufactured from a metal such as steelor other metal alloy materials. However, traditional metal rebars have anumber of significant disadvantages. Most concrete structures areexposed to moisture, acids and chlorine containing chemicals whichslowly corrodes the metal over time. Thus, the lifetime of metal rebarsis limited. Metal rebars are manufactured in a mill or other productionfacility in the desired end shape and then shipped, at high cost, to theconstruction site. By having prescribed lengths, metal bars must be cutto length at the construction site which causes waste and additionalcost. They cannot be manufactured at a remote location, such as theconstruction site. Further, metal rebars can only be shaped or formed atthe construction site with significant effort to fit the varying needsarising during the course of construction.

In addition to metal reinforcing bars, rebars have also been made fromreinforced thermosetting polymer materials. The thermoset polymers arereinforced with fibers to provide the required strength for structuralsupport. These thermoset polymer rebars offer the advantage of beinggenerally more resistant to corrosion than their metal counterparts. Inaddition, they generally weigh less than metal rebars, thereby reducingshipping costs.

Once a thermoset polymer is fixed in a particular shape, that fixedshape cannot be changed. In other words, a thermoset polymer may not beformed or manipulated once the polymer has cured. Accordingly, athermoset rebar is not formable in the sense that the rebar can have itsshaped changed on the job site to correspond with the changingconstruction environment. In addition, rebars of thermosetting polymersmust be made in a manufacturing facility. Remote production is notpossible as the thermoset rebar must be manufactured to its finaldimensions immediately.

Accordingly, there remains a need for a corrosion resistant reinforcingbar for structural support in construction applications which isformable after the bar has been manufactured and which is capable ofbeing manufactured in remote locations such as at a construction site.

SUMMARY OF THE INVENTION

This need is met by the present invention wherein a formablereinforcement bar is provided. The formable reinforcement bar of thepresent invention may be shaped or formed on the construction site afterthe reinforcing bar has been produced. This provides the rebar of thepresent invention a versatility in usage which the reinforcing bars ofthe prior art cannot achieve. In addition, the rebar of the presentinvention can be produced from pre-preg layers in remote locations suchas the construction site, thereby providing additional versatility andreduced cost over the reinforcing bars of the prior art.

Thus, in accordance with the present invention a formable reinforcingbar for structural support is provided. The formable reinforcement barcomprising a body portion having at least one layer of a fiberreinforced thermoplastic polymer material. The layer has multiplecontinuous fibers completely embedded in the thermoplastic material. Thefibers are preferably glass fibers, carbon fibers, aramid fibers orpolyamide fibers, with glass fibers most preferred. The continuousfibers preferably comprise about 20% to about 80% of the total volume ofthe body portion, and more preferably about 40% to about 60% of thetotal volume, of the reinforcing bar.

In one embodiment of the invention, the reinforcement bar has a tensionload capacity of at least about 500 pounds, preferably at least about1,000 pounds, and most preferably about 5,000 pounds, and isthermoformable after the reinforcement bar is produced. In addition, thereinforcement bar may be bent, twisted or helically spiralled. Thereinforcement bar may be most any desired shape such as rectangular,square, angled or circular.

The body portion may be formed from at least two layers which arelaminated together. The layers are preferably strips of thermoplasticmaterial having continuous fibers completely embedded therein or bundlesof continuous fibers completely coated with a thermoplastic material.The body portion may include at least one outer face which is textured.The texturing may be accomplished by knurling the outer face,impregnating the outer face with particles, or including raised memberson the outer face. Further, the thermoplastic material may includeparticles or flakes of a metal, polar or magnetic material incorporatedtherein.

In accordance with an additional aspect of the present invention, thereis provided a structure supported with the reinforcing bar of thepresent invention. The supported structure comprises a compositematerial having a reinforcing bar embedded therein. The reinforcing barcomprises a body portion having at least one layer of a thermoplasticpolymer material. The layer has multiple continuous fibers completelyembedded in the thermoplastic material. The continuous fibers arepreferably about 20% to about 80% of the total volume of the bodyportion, and more preferably about 40% to about 60% of the total volumeof the body portion. Further, the reinforcement bar has a tension loadcapacity of at least about 500 pounds, more preferably at least about1,000 pounds and most preferably about 5,000 pounds.

The composite material is preferably Portland cement concrete, asphaltconcrete or polymer concrete. The continuous fibers are preferably glassfibers, carbon fibers, aramid fibers or polyamide fibers, with glassfibers being the most preferred. The body portion may be at least twolayers laminated together. In addition, the layers are preferably stripsof thermoplastic material having continuous fibers completely embeddedtherein or bundles of continuous fibers completely coated with athermoplastic material. The body portion may include at least one outerface which is textured.

In accordance with another aspect of the present invention, a processfor producing a formable reinforcing bar is provided. The processcomprises providing at least two layers comprising a thermoplasticpolymer material having multiple continuous fibers completely embeddedin the thermoplastic polymer material. The layers are passed through apre-treating zone to pre-treat the layers. Next, the pre-treated layersare passed through a lamination zone where the layers are brought intocontact with each other and consolidated to form a laminated bodyportion. The body portion is passed through a post-treating zone wherethe body portion is cooled to form a reinforcing bar which isthermoformable after it is produced.

The continuous fibers are preferably glass fibers, aramid fibers, carbonfibers, or polyamide fibers with glass fibers being the most preferred.The continuous fibers may comprise about 20% to about 80% of the totalvolume of the body portion, and preferably about 40% to about 60% of thetotal volume of the body portion. In addition, the layers are preferablystrips of thermoplastic material having continuous fibers completelyembedded therein or bundles of continuous fibers completely coated withthermoplastic material.

The process of the present invention may further include the steps ofcutting the reinforcing bar to a desired length and/or providing textureto at least one outer face of the body portion. The texture may beprovided by knurling the outer face, impregnating the outer face withparticles or including raised members on the outer face. The heatingstep may be accomplished by supplying heated forced gas, infraredradiation, microwave radiation, radio waves, or induction heating. Anadditional step in the process may include the step of thermoforming thereinforcing bar after the bar is produced. The step of thermoforming maycomprise heating and twisting or bending the reinforcing bar. Thereinforcing bar may also be produced at a remote location.

The step of pre-treating the thermoplastic layers may comprise a heatingstep. After the heated layers are laminated, they are passed to apost-treating zone wherein the body portion is cooled. Alternatively,the pre-treating step may comprise the application of a solvent to thethermoplastic layers. Once compressed, the solvent is evaporated orotherwise allowed to dry in a post-treating step when the thermoplasticlayers are laminated or bonded together.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the formable reinforcing bar of thepresent invention.

FIG. 2 is an exploded perspective view of the formable reinforcing barof the present invention.

FIG. 3 is a perspective view of the formable reinforcing bar the presentinvention after being thermoformed into a spiral shape.

FIG. 4 is a schematic view in elevation of the process by which theformable reinforcing bar of the present invention is produced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention comprises a formable reinforcement bar or rebarfor providing structural support in construction applications. Thepresent invention involves rebars of thermoplastic materials.Thermoplastic materials may be easily softened by the application ofheat and shaped. When cooled, the thermoplastic rigidly assumes the newposition. This provides a versatility unmatched by prior artreinforcement bars, as the rebars of the present invention may betailored to fit exact specifications without difficulty or delay. Inaddition, the formable rebar of the present invention may be produced atremote locations such as the construction site. Production at a remotelocation would significantly reduce the cost of shipping and waste fromthat of transporting preformed reinforcement bars.

Referring to FIG. 1, the formable reinforcing bar 10 of the presentinvention is shown. The rebar 10 comprises a body portion 12. The bodyportion 12 has at least one layer of a thermoplastic polymer material 14with multiple continuous fibers 16 completely embedded in thethermoplastic material. Preferably, the body portion 12 is formed frommultiple thermoplastic layers 14. Of course, one of ordinary skill inthe art will recognize that the number of layers employed will dependupon the desired application for rebar 10.

The thermoplastic material in thermoplastic layers 14 may generally bemost any polymer of the general class of thermoplastic polymers. Infact, the specific thermoplastic material employed will in many casesdepend upon the end use and location of the rebar 10. Variousthermoplastic materials have varying properties such as resistance tocorrosion, stiffness or strength. Preferably, the thermoplastic materialis compatible with the building material into which it will beincorporated, such as concrete or the like. Examples of suitablethermoplastic materials which can be employed in the present inventioninclude high density polyethylene, polypropylene and copolymers ofpolypropylene with various materials, polyphenylene sulfide andpolyvinyl chloride.

Fibers 16 are continuous fibers of filaments which are suitable forincorporation into the thermoplastic material 14. Continuous fibers, asintended herein, are fibers produced from drawing processes and whichhave not been cut to specific lengths. However, non-continuous fibers,such as those which have been cut to length or formed in a rotaryprocess, may also be included in the thermoplastic material along withthe continuous fibers. While most any continuous fiber may be employed,glass fibers, carbon fibers, aramid fibers or polyamide fibers arepreferred, with continuous glass fibers being the most preferred.

Continuous fibers 16 are included to provide strength to thethermoplastic material 14. Thus, the fibers 16 are embedded in thethermoplastic material or, in other words, completely encapsulated withthermoplastic material. Complete encapsulation of the fibers 16 by thethermoplastic material is desired so as to provide the greatest degreeof strength possible from the materials present. However, too high acontent of fibers 16 in body portion 12 reduces the amount ofthermoplastic polymer in the body portion 12. As a result, not all thefibers are sufficiently coated with the thermoplastic material therebyactually reducing the strength and environmental resistance of thelayer. In addition, the difficulty of producing the rebar 10 isincreased due to increased difficulty in coating the fibers. On theother hand, too low a content of fibers reduces the strength of therebar to unsatisfactory levels.

Thus, the volume of continuous fibers 16 in body portion 12 is selectedto impart an optimum balance between strength and ease of production andperformance. Preferably, continuous fibers 16 comprise from about 20% toabout 80% of the total volume of body portion 12 with the remainder ofeach layer 14 being the thermoplastic material encapsulating thecontinuous fibers 16. Most preferably, the continuous fibers 16 comprisefrom about 40% to about 60% of the total volume of the body portion 16.

The combination of thermoplastic material and continuous fibers 16 inthe reinforcement bar 10 of the present invention must be sufficient toprovide the rebar 10 with a tension load capacity of at least about 500pounds. Tension load capacity is a measure of the strength of a rebar.Tension load capacity is a measure of the amount of load at which aparticular rebar would fail when loaded with tension. Tension loadcapacity is measured by placing a rebar in any number of availabletesting apparatuses and applying force to each end of the rebar inopposite directions. The amount of force required to cause the rebar tofail is then the tension load capacity. A description of a suitabletesting procedure can be found, for example, in ASTM D638. Preferably,the tension load capacity of the rebar of the present invention of atleast about 500 pounds, more preferably at least about 1,000 pounds, andmost preferably at least about 5,000 pounds.

The thermoplastic material comprising layer 14 may also includeparticles or flakes incorporated into the thermoplastic material. Theincorporated particles or flakes enhance the heating ability of thethermoplastic material, thus, allowing the thermoplastic to heat morequickly and/or more uniformly for re-forming. The incorporated flakesand particles may be selected from metal or alloy materials, polarmaterials or magnetic materials. Thus, the thermoplastic material willheat more quickly if alternative heating methods, such as infrared ormicrowave radiation, radio waves, or induction heating are used.

As discussed previously, one of the many advantages of the rebar 10 ofthe present invention lies in that the rebar 10 is formable after it hasbeen produced. That is, once the rebar is manufactured, it may still beformed into various shapes easily by the application of heat and forceto the thermoplastic. This is in extreme contrast to thermoset polymerrebars. Once a thermoset polymer rebar has been produced, its shapecannot be changed, but rather is fixed in the manufactured shape. Metalor alloy rebars can be re-formed after manufacture only after theapplication of extreme temperatures or forces. They may not be easilyre-formed by the mere application of relatively low temperatures to thethermoplastic material as in the present invention.

The rebar of the present invention may be re-formed after manufacture.For instance, the rebar may be bent or twisted as shown in FIG. 3 forapplication in the construction site. Alternatively, a straight rebarmay be provided with a hook on one or both ends. The rebar 10 may bere-formed by a thermoforming process or, in other words, the applicationof heat. To re-form the rebar, the thermoplastic material in the area tobe formed must simply be heated, for instance by a heat gun or othermeans, to the point at which the thermoplastic material employed becomessoftened or pliable, commonly known as the softening point temperature.The heated rebar then is simply shaped then allowed to cool. There-formed rebar is then fixed in the new shape and can be immediatelyemployed in the construction site.

The ability to be re-formed provides a previously unknown versatility tothe rebar 10 of the present invention. Previously, a thermoset or metalrebar was received at the construction site in a pre-formed shape. Thatshape was then made to fit into the structure to which it was to providesupport as best as possible. In many instances, the rebar was cut andthe unused portion discarded, increasing costs and waste. The rebar 10of the present invention may be re-formed and tailored to fit specificapplications by workers on the construction site. Accordingly, there isless waste and, thus, lower cost involved than with thermoset or metalrebars.

The rebar 10 of the present invention may also include texturing on atleast one outer face of the body portion 12. Texture on at least oneouter face provides improved bonding between the material into which therebar is placed and the rebar itself. Texturing may be achieved by anynumber of various methods including knurling the outer face or faces,impregnating particles into the outer face or faces, including raisedmembers on the outer face or faces, or embossing a textured surface.

The present invention also includes a process for producing the formablerebar 10 of the present invention. As mentioned previously, the formablerebar comprises at least one layer 14 of thermoplastic material. Thus,while the rebar 10 may comprise a single layer, the rebar 10 preferablycomprises at least two layers and more preferably multiple layers ofthermoplastic material. The layers 14 preferably comprise strips ofthermoplastic material having continuous fibers completely embeddedtherein, or bundles of continuous fibers completely coated with thethermoplastic material.

To produce the strips or bundles as the pre-preg layers 14, the stripsor bundles may be produced by numerous processes which will produce athermoplastic having fibers embedded in the polymer material.Preferably, the strips or bundles are produced by impregnating multiplestrands of fibers with thermoplastic resins through a die as describedin U.S. Pat. No. 4,937,028, the disclosure of which is hereinincorporated by reference, or by heating multiple strands ofpreimpregnated fibers and consolidating them through a die or bycompression rolls, or other means in the art to form strips ofreinforced thermoplastic.

Turning now to FIGS. 2 and 4, the preferred lamination process forproducing the formable rebar 10 of the present invention is shown. Theprocess involves providing at least two, and preferably multiple, fiberreinforced thermoplastic layers 14. While the layers 14 may be of anyknown dimensions, the layers are preferably from about 1/32 inch toabout 1/4 inch in thickness by about 0.5 to 2 inches in width. Ofcourse, the cross-sectional area of the formed rebar 10 will depend uponthe desired end use dimensions and can be varied by varying the numberand width of layers 14 employed in the rebar 10. The layers 14 arepreferably supplied on spools 18 of wound, continuous strips or bundlesas discussed above. The continuous thermoplastic layers are unwound fromthe supply spools 18 and passed into a pre-treating zone 20.Pre-treating zone 20 provides a pre-treating step to prepare thesurfaces of the layers to be laminated together.

Pre-treating the surfaces of the layers 14 to be laminated together maycomprise either the application of heat or of a suitable solvent. Thepre-treating step of heating may be accomplished by the application ofheated forced gas, infrared radiation, microwave radiation, inductionheating or radio waves, all of which are well-known in the art ofheating polymers. The thermoplastic layers 14 are heated to the point atwhich the thermoplastic material becomes pliable and bondable.

Alternatively, the pre-treating step may comprise the application of asuitable solvent to the surfaces of the layers to be laminated. Thesolvent, once applied, dissolves or solubilizes a small amount ofthermoplastic material on the surface of the layers. Suitable solventsmay varying depending upon the particular thermoplastic employed butinclude, among other, methylene chloride.

The individual layers 14 are brought into contact with each other eitherduring or after the pre-treating stage. Once in contact, the pre-treatedlayers 14 are passed into a lamination zone 24 where the pre-treatedlayers 14 are consolidated by a series of compression rollers 26 to formbody portion 12. The pre-treated layers 14 may be aligned eithervertically, one on top of the other, or horizontally in a side-by-sidearrangement. The pre-treated layers, once compressed together, bond witheach other to form the integral body portion 12 of the rebar 10.

The body portion 12, once formed, is passed to a post-treating zone 28where the bonds between the pre-treated layers 14 of body portion 12 areallowed to set. The post-treating zone 28 is preferably merely a coolingstage where the layers if heated may be cooled or a solvent if appliedis allowed to evaporate while the polymer material sets. During thepost-treating step, the process may also include the additional step ofcutting the body portion 12 into desired lengths of the rebar 10 toeliminate waste. The cutting may accomplished by any known cutting meansincluding a cutting blade (not shown). Lastly, the thermoplasticmaterial may be pulled through the process by tension or pulling wheels30 to provide a constant rate of material passing through the process ifthe consolidation rolls 26 do not provide the pulling force.

The process may also include the additional step of providing texture 32onto at least one outer surface of the body portion 12. The step oftexturing may include various known means of providing texturing topolymer materials, but preferably includes knurling at least one outersurface by various means such as making cross-hatched, diagonal orpatterned cuts or channels into the outer surface. The externaltexturing would most likely be imparted through the transfer of atextured surface on the compression rolls 26. In addition, the step ofproviding texture may also preferably include heating or softening theouter surface thermoplastic material then embedding particles of variousmaterials in the softened material. The step of texturing may alsoinclude providing raised members on at least one outer face.

One of the many advantages of the present invention includes the abilityto produce the rebar 10 at remote locations such as the on theconstruction site. As the process does not require the melting of metalsor alloys, or a pultrusion step as in thermoset polymers, both of whichmust be conducted in a formal production facility, the process may beconveniently and easily conducted in remote locations, as well as, in aproduction facility. This ability for remote production provides asignificant advantage over the prior art processes and rebars. The costof shipping a pre-formed rebar, as in the prior art, is much greaterthan the cost of shipping the pre-preg layers 14 of the presentinvention. Thus, shipping the pre-preg layers then forming the rebar 10of the present invention then producing the rebars 10 on theconstruction site will provide a significant cost savings to the userover the rebars of the prior art.

The present invention also includes a combination supported structureand reinforcing bar. The rebar of the present invention is designed forinclusion into structures under construction to provide support to thestructure once completed. Such structures commonly include walls andfloors in buildings, roadbeds, bridges, and various other structures.The rebars of the present invention are embedded into materials such asconcrete and asphalt that are commonly used to construct the supportedstructures. Thus, an aspect of the present invention includes asupported structure comprising a composite material having the rebar ofthe present invention embedded in the construction material. Theconstruction material in which the invention is incorporated as areinforcing or supporting member is preferably Portland cement concrete,asphalt concrete or polymer concrete.

Having described the invention in detail and by reference to thepreferred embodiment thereof, it will be apparent that modifications andvariations are possible without departing from the scope of theinvention which is defined in the appended claims.

I claim:
 1. A process for producing a formable reinforcing bar comprising:providing at least two layers, said layers comprising a thermoplastic polymer material having multiple continuous fibers completely embedded in said thermoplastic polymer material; passing said layers through a pre-treating zone to pretreat said layers; bringing said pre-treated layers into contact; passing said pre-treated layers through a lamination zone wherein said layers are compressed to form a laminated body portion, and passing said body portion to a post-treating zone whereby said body portion is post-treated thereby forming a reinforcing bar which is thermoformable after said reinforcing bar is produced.
 2. The process as claimed in claim 1 wherein said continuous fibers are glass fibers, aramid fibers, carbon fibers, or polyamide fibers.
 3. The process as claimed in claim 2 wherein said continuous fibers are glass fibers.
 4. The process as claimed in claim 1 wherein said layers are strips of thermoplastic material having continuous fibers completely embedded therein.
 5. The process as claimed in claim 1 wherein said layers comprises bundles of continuous fibers completely coated with thermoplastic material.
 6. The process as claimed in claim 1 further including the step of providing texture to at least one outer face of said body portion in said lamination zone.
 7. The process as claimed in claim 6 wherein said step of providing texture comprises knurling said outer face, impregnating said outer face with particles or including raised members on said outer face.
 8. The process as claimed in claim 1 further including cutting said reinforcing bar to a desired length.
 9. The process as claimed in claim 1 further including the step of thermoforming said reinforcing bar after said bar is produced.
 10. The process as claimed in claim 9 wherein said step of thermoforming comprises heating and twisting or bending said reinforcing bar.
 11. The process as claimed in claim 1 wherein said reinforcing bar is produced at a remote location.
 12. The process as claimed in claim 1 wherein said continuous fibers comprise about 20% to about 80% of the total volume of said body portion.
 13. The process as claimed in claim 12 wherein said continuous fibers comprise about 40% to about 60% of the total volume of said body portion.
 14. The process as claimed in claim 1 wherein said step of pre-treating comprises heating said layers and said step of post-treating comprises cooling said laminated body portion.
 15. The process as claimed in claim 14 wherein said step of heating is accomplished by supplying heated forced gas, infrared radiation, microwave radiation, radio waves or induction heating.
 16. The process as claimed in claim 1 wherein said step of pre-treating comprises applying a solvent to said layers and said step of post-treating said laminated body portion comprises allowing said solvent to evaporate or otherwise dry. 